FAIRFIELD, Conn. – Fairfield expects to spend nearly $4.2 million to remove potential contaminants and make renovations at Osborn Hill School, according to the latest figures.

Last summer, inspectors found concentrations of polychlorinated biphenyls (PCBs) in Osborn Hill School that exceeded the U.S. Environmental Protection Agency’s limits for a school. Since then Fairfield has been working to remove the materials from the school. So far the process has cost about $820,000.

Most of the removal work has been finished, except for the school’s gymnasium, where the highest concentrations of PCBs were found. The library was cleared of PCBs over holiday break and will reopen to students Friday.

“Other than the gym…we will be fully operational by Friday,” Schools Superintendent David Title said Wednesday. “The good news is that while this was expensive, it worked.”

This summer the town will need to clean up and renovate the gymnasium to get rid of the last traces of PCBs. The school will also get new windows in most of its classrooms, which was the initial construction project that turned up the chemicals. PCBs were found in the caulk lining the windows and doors as well, but since they were not airborne the school was able to open without removing them.

The gymnasium and window project is expected to cost about $3.37 million. The renovations will also include adding an enclosed walkway to Osborn Hill’s annex, which was included in the project to increase the school’s safety.

“We really limited the scope to the window project, and what we really needed to do in that gymnasium,” Title said. “We’re really trying to keep the dollars as low as possible, knowing that there are a number of other projects stacked up.”

The Board of Selectmen approved a $4.2 million bond package to cover the current cleanup costs and this summer’s renovations. The Board of Finance and the Representative Town Meeting will vote on the plans later this month.